JP2012237811A - Illumination device, projection video display device, and light deflecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device that illuminates an illumination object area (image forming area) without causing a conspicuous speckle noise, and to provide a projection video display device thereof.SOLUTION: The illumination device includes a light source 11 for emitting coherent light, a light deflecting optical element 21 having different light deflection angle according to a light incident position, and moving means for temporally moving the light deflecting optical element 21. The coherent light emitted from the light deflecting optical element 21 which is moved by the moving means illuminates the illumination object area by temporally superposing the illumination while temporally changing an incident angle to each point in the illumination object area.

Description

  The present invention relates to an illumination device that uses coherent light such as laser light, a projection-type image display device that illuminates a light modulation element using the coherent light as a light source and projects an image on a screen, and an optical deflection device used therefor It is about.

  2. Description of the Related Art A projector (projection-type image display device) is known in which illumination light from a light source is imaged using a light modulation element (micro display) such as liquid crystal or MEMS and projected onto a screen. Among such projectors, a projector using a white light source such as a high-pressure mercury lamp as the light source is known, and an image obtained by illuminating a two-dimensional light modulation element such as a liquid crystal is magnified by a projection optical system. The image is projected above.

  However, high-intensity discharge lamps such as high-pressure mercury lamps have a relatively short life and need to be frequently replaced when used in projectors. In addition, there is a drawback that the apparatus itself is increased in size. Furthermore, the specification of a high-pressure mercury lamp that uses mercury is not preferable from the viewpoint of environmental load. In order to eliminate such drawbacks, a projector using laser light as a light source has been proposed. The semiconductor laser has a longer life than a high-pressure mercury lamp or the like, and the entire apparatus can be reduced in size.

  Thus, since the laser beam expected as the next-generation light source of the projector is excellent in straightness, it is considered that the light incident efficiency can be improved as compared with the LED or the like. However, when laser light is used as a light source, there is a drawback that speckle noise is generated due to high coherence and it is difficult to view an image.

  Speckle noise is speckled noise caused by interference of light scattered from minute irregularities on the surface of the irradiation object when coherent laser light is used as the light source. As well as causing physiological discomfort to the observer. In order to reduce this speckle noise, various attempts have been made, such as vibrating the diffusion plate through which the laser beam passes, expanding the wavelength spectrum of the laser spectrum, and vibrating the screen itself that is the target of the laser beam irradiation. . As an attempt to reduce such speckle noise, Patent Document 1 discloses a non-speckle display device that reduces speckle noise by rotating a diffusion element through which coherent light passes.

Japanese Patent Laid-Open No. 6-208089

  However, in the speckle noise reduction method disclosed in Patent Document 1, speckle noise (interference pattern) generated before reaching the diffusing element can be averaged, but the incident ray angle from the diffusion center to the screen is on the screen. Since it is invariant at any point, the light scattering characteristic of each point on the screen becomes constant, and as a result, there is a problem that the effect of removing speckle noise generated on the screen is hardly obtained.

Such speckle caused by coherent light is a problem not only in a projection-type image display device (projector) that uses coherent light as a light source but also in various illumination devices that use coherent light.

  An object of the present invention is to provide an illuminating device that suppresses speckles generated when coherent light is used as a light source, and a projection-type image display device using such an illuminating device.

The lighting device according to the present invention includes:
A light source that emits coherent light;
A deflecting optical element having a different deflection angle depending on the incident position;
A moving means for moving the deflecting optical element over time;
The coherent light emitted from the deflecting optical element moved by the moving means illuminates the illuminated area by overlapping with time, and changes the incident angle to each point of the illuminated area with time. It is characterized by lighting.

  Furthermore, in the illumination device according to the present invention, the coherent light emitted from each point of the deflection optical element moved by the moving means always illuminates the entire illuminated area.

  Furthermore, in the illumination device according to the present invention, the deflecting optical element is a light-transmitting substrate having a different thickness depending on an incident position.

  Furthermore, in the illumination device according to the present invention, the deflection optical element is formed with diffraction gratings having different pitches of interference fringes depending on the incident position.

  Furthermore, the illumination device according to the present invention is characterized in that the moving means moves the deflection optical element over time by rotation.

  Furthermore, the illuminating device according to the present invention is characterized by comprising beam shaping means arranged between the light source and the deflecting optical element and uniformizing the intensity distribution of the coherent light emitted from the light source.

The projection display apparatus according to the present invention is
A light source that emits coherent light;
A deflecting optical element having a different deflection angle depending on the incident position;
Moving means for moving the deflection optical element over time;
A light modulation element having an image forming region on which an image is formed;
A projection optical system that projects an image of the light modulation element onto a screen, and the coherent light emitted from the deflecting optical element moved by the moving unit illuminates the image forming region with time lapse. The illumination is performed by changing the incident angle to each point of the image forming region with time.

An optical deflecting device according to the present invention includes:
A deflecting optical element that receives coherent light and has a different deflection angle depending on the incident position;
A moving means for moving the deflecting optical element;
The coherent light emitted from the deflecting optical element moved by the moving means illuminates the illuminated area by overlapping with time, and changes the incident angle to each point of the illuminated area with time. It is characterized by lighting.

  According to the projection type image display apparatus of the present invention, the coherent light is deflected by the deflecting optical element that is moved with time by the moving means, so that the illumination light emitted from the deflecting optical element can pass through the illuminated area over time. In addition to illuminating, the incident angle to each point in the illuminated area is changed over time, and speckles generated in the illuminated area change over time, making it invisible to the observer It becomes possible to make it. Furthermore, in the projection type image display apparatus of the present invention, speckles generated on the screen can be effectively suppressed by irradiating the screen at different angles in time.

The figure which shows the structure of the projection type video display apparatus provided with the illuminating device which concerns on embodiment of this invention. The figure which shows the mode of the illumination in the illuminating device which concerns on embodiment of this invention. The figure which shows the structure of the deflection | deviation optical element (rotary type) which concerns on embodiment of this invention. The figure which shows the structure of the deflection | deviation optical element (translation type) which concerns on other embodiment of this invention. The figure which shows the structure of the illuminating device which concerns on other embodiment of this invention.

  Now, the light deflection apparatus, the illumination apparatus, and the projection display apparatus according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a projection-type image display device including an illumination device according to an embodiment of the present invention. Note that the drawings described below are schematic views and may differ from actual shapes, dimensions, and arrangements.

  The projection-type image display device 10 of this embodiment includes an illumination device, a light modulation element 31 for forming an image, a projection optical system 32 that projects an image formed by the light modulation element 31 onto a screen 41, and the like. Yes. In the figure, the screen 41 on which an image is projected is an XY plane, and an axis perpendicular to the XY plane is a Z axis. As the screen 41, either a reflective screen for observing an image reflected by the screen 41 or a transmissive screen for observing an image transmitted through the screen 41 can be used.

  The illuminating device of this embodiment includes a light source 11, a deflecting optical element 21, and a moving unit that moves a deflecting optical element (not shown). Further, in the illuminating device, the optical deflecting device is configured by the other configuration (the deflecting optical element 21 and the moving means) excluding the light source 11.

  As the light source 11, a light emitting element 111 such as a semiconductor laser that emits laser light as coherent light is used. The light source 11 of the present embodiment is configured to include a beam expander 112 disposed at the subsequent stage of the light emitting element 111. The beam expander 112 is configured by a combination of convex lenses 112a and 112b, and is enlarged to a diameter sufficient to illuminate the image forming region of the light modulation element 31. In addition to such a configuration, an appropriate form such as a combination of a concave lens and a convex lens can be adopted. The coherent light emitted from the light source 11 to the deflecting optical element 21 is preferably emitted as parallel or substantially parallel coherent light. It is possible to illuminate each point of the deflection optical element 21 arranged in the subsequent stage under the same conditions.

  The coherent light emitted from the light source 11 illuminates the deflection optical element 21. In addition, it is preferable to provide beam shaping means for uniforming the intensity distribution in the cross-sectional direction of the coherent light emitted from the light source 11. As a design example, it is possible to illuminate the light modulation element with a uniform intensity by providing a beam shaping means after the beam expander 112. The beam shaping means is an element that changes the cross-sectional intensity distribution of the beam by an effect such as refraction or diffraction, and a hologram or a refractive element is used.

  The deflection optical element 21 is an optical element having a different deflection angle that is emitted according to the incident position of light. In the present embodiment, the deflection optical element 21 has a disk shape that can rotate around the rotation shaft 21a, and has a thickness at each location. Is changed, a curved surface is formed on the back surface (surface on the screen 41 side). Further, the surface on which coherent light from the light source 11 is incident is formed as a flat surface, and is formed of a substrate made of a light-transmitting material. The direction of the coherent light incident from the light source 11 is temporally changed by rotating the disc-shaped deflecting optical element 21 around a rotation axis 21a in the Z-axis direction by a moving means such as a motor.

  FIG. 3 shows a schematic diagram of the deflection optical element 21 of the present embodiment when viewed from the Z direction. As shown in this figure, the deflecting optical element 21 having a disk shape has convex surfaces 211a and concave surfaces 211b alternately formed in the circumferential direction. The direction of the incident coherent light is changed over time by illuminating the illumination area indicated by the broken line with the coherent light from the light source 11 while rotating the deflecting optical element 21 by the moving means around the rotation axis 21a. Making it possible. The curved surface formed by the convex surface 211a and the concave surface 211b formed on the deflection optical element 21 is preferably formed so as to continuously change. It is possible to smoothly change the deflection direction.

  In the present embodiment, the thickness of the deflecting optical element 21 is changed in this way, and the convex surface 211a and the concave surface 211b are formed on the back surface side. However, the form of the deflecting optical element 21 is not limited to this. As long as the direction of the incident coherent light is changed over time by being moved by the moving means, it can take any appropriate form. For example, the change in thickness at each location may be formed on the surface (surface on the light source 11 side) or may be formed on both surfaces. Moreover, it is good also as deflecting by forming a diffraction grating. In that case, the change in the deflection direction is realized by changing the pitch of the interference fringes forming the diffraction grating toward the circumferential direction of the deflection optical element 21.

  In FIG. 1, coherent light incident from a light source 11 becomes deflected light La whose direction changes in time by a deflecting optical element 21 rotated by a moving means, and an image forming area of a light modulation element 31 as an illuminated area. Illuminate. In the drawing, the states of the deflected light La (t1) and La (t3) near the outermost end and the deflected light La (t2) in the direction perpendicular to the light modulation element 31 are shown. The light La moves continuously or intermittently over time between La (t1) and La (t3).

  The light modulation element 31 is a display having an image forming area in which an image is formed based on a video signal. In this embodiment, a transmissive liquid crystal display element is used. As the light modulation element 31, in addition to such a transmission type, a reflection type such as MEMS can be used. The deflected light La from the deflecting optical element 21 enters the light modulation element 31 while changing the incident angle with time, and is converted into modulated light Lb based on the image displayed in the image forming area.

  The projection optical system 32 enlarges and converts the modulated light Lb from the light modulation element 31 into the video reproduction light Lc and projects it onto the screen 41. In the present embodiment, a diaphragm 33 is provided downstream of the projection optical system 32.

  Now, the principle and the like of the illumination device 20 which is a main configuration for suppressing speckles in the projection display apparatus 10 will be described in detail. FIG. 2 shows how the deflection light La emitted from the light deflection element 21 according to the embodiment of the present invention changes with time.

FIGS. 2A to 2C show the state of the deflected light La that changes as the deflecting optical element 21 moves. In this figure, the disk-shaped deflection optical element 21 is shown in an extended form, and the curved surface of the deflection optical element 21 is shown in an easily understandable manner. As shown in this figure, the deflected light La from each point of the deflecting optical element 21 changes its direction of emission as time passes, and at any time the image forming area of the light modulating element 31 Illuminate at least some areas. Further, the deflected light La emitted from each point illuminates the entire image forming region while temporally changing the incident angle while overlapping and illuminating the image forming region as the illuminated region over time. . Regardless of the deflection direction of the deflecting optical element 21, the illuminated area is preferably set to an area that is always illuminated in order to achieve uniform brightness and improve light utilization efficiency.

  Returning to FIG. 1, the modulated light Lb modulated by the light modulation element 31 is magnified by the projection optical system 32 and projected onto the screen 41 as the image reproduction light Lc, and the reflected or transmitted image is observed by the observer. Let At this time, the coherent light scattered on the surface of the screen 41 interferes with each other to cause speckle. However, in the present embodiment, since the coherent light is deflected by the deflecting optical element 21 rotated by the moving means, as a result, the incident angle of the image reproduction light Lc projected on the screen 41 is changed with time, and this speckle. Is very inconspicuous.

  At the point P1 on the screen shown in FIG. 1, for example, the video reproduction light Lc (t1) at time t1 and the video reproduction light Lc (t3) at time t3 are irradiated at different incident angles. The same applies to other points P2 shown in the figure and other points not shown, and the image reproduction light Lc projects an image on the screen 41 while temporally changing the incident angle. Therefore, speckles formed on the screen in a very short time are also averaged in time within the visual response time and projected onto the screen 41 by the image reproduction light Lc being irradiated at different incident angles depending on the time. This is not sufficiently conspicuous for an observer who observes an image.

  As described above, the projection type image display device and the illumination device used therefor have been described using the present embodiment in FIGS. 1 and 2, but the shape of the deflection optical element 21 is limited to the disk shape described in FIG. 3. Instead, various shapes can be employed.

  FIG. 4 is a diagram showing the deflecting optical element 21 in a rectangular shape, and the moving means reciprocates the deflecting optical element 21 in the horizontal direction. Further, convex surfaces 211a and concave surfaces 211b are alternately formed in the moving direction of the deflecting optical element 21. By illuminating a predetermined illumination area with the light source 11, the direction of the light emitted from the deflection optical element 21 can be changed over time. Also in this embodiment, it is possible to use a diffraction grating formed so that the pitch of the interference fringes changes in the moving direction instead of the concave surface 211a and the convex surface 211b.

  In the embodiment described with reference to FIG. 1, the deflected light La emitted from the deflecting optical element 21 is directly incident on the image forming area of the light modulation element 31 as the illuminated area. An imaging optical system may be provided between the element 21 and the illuminated area.

  FIG. 5 shows an embodiment in which the imaging optical system 22 is arranged between the deflection optical element 21 and the illuminated area, and shows the configuration from the deflection optical element 21 to the light modulation element 31 in the projection display apparatus 10. Has been. The imaging optical system 22 of the present embodiment includes a first optical element 22a and a second optical element 22c having a condensing function, and a diaphragm 22b disposed therebetween. As the deflection optical element 21 moves, the direction in which the deflected light La is emitted is changed from La (t1) to La (t3). However, as in this embodiment, the imaging optical system is changed. By using 22 to form an image in the image forming region of the light modulation element 31, the deflecting optical element 21 can be provided away from the light modulation element 31, and the design is facilitated.

  As described above, according to the present embodiment, an illumination device in which speckle noise is not noticeable, and a projection-type image that can provide an image in which speckle noise is not noticeable by illuminating the light modulation element 31 with the illumination device. A display device can be provided.

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Projection type image display apparatus 11 ... Light source 111 ... Light emitting element 112 ... Beam expander 112a, 112b ... Convex lens 21 ... Deflection optical element 21a ... Rotating shaft 211a ... Convex surface 211b ... Concave surface 22 ... Imaging optical system 22a ... First optical element 22b ... Aperture 22c ... Second optical element 31 ... Light modulation element 32 ... Projection optical system 33 ... Aperture 41 ... Screen

Claims (8)

A light source that emits coherent light;
A deflecting optical element having a different deflection angle depending on the incident position;
A moving means for moving the deflecting optical element;
The coherent light emitted from the deflecting optical element moved by the moving means illuminates the illuminated area by overlapping with time, and changes the incident angle to each point of the illuminated area with time. A lighting device characterized by illuminating. The illuminating device according to claim 1, wherein coherent light emitted from each point of the deflecting optical element moved by the moving means illuminates the entire illuminated area. The illumination device according to claim 1, wherein the deflecting optical element is a light-transmitting substrate having a different thickness depending on an incident position. The illumination device according to claim 1, wherein the deflection optical element is formed with a diffraction grating having a different pitch of interference fringes depending on an incident position. The illumination device according to any one of claims 1 to 4, wherein the moving unit moves the deflection optical element by rotation. The illumination device according to any one of claims 1 to 5, wherein a beam shaping unit is disposed between the light source and the deflection optical element. A light source that emits coherent light;
A deflecting optical element having a different deflection angle depending on the incident position;
Moving means for moving the deflection optical element;
A light modulation element having an image forming region on which an image is formed;
A projection optical system that projects an image of the light modulation element onto a screen, and the coherent light emitted from the deflecting optical element moved by the moving unit illuminates the image forming region with time lapse. A projection type image display apparatus, wherein illumination is performed by changing an incident angle to each point of the image forming region with time. A deflecting optical element that receives coherent light and has a different deflection angle depending on the incident position;
A moving means for moving the deflecting optical element;
The coherent light emitted from the deflecting optical element moved by the moving means illuminates the illuminated area by overlapping with time, and changes the incident angle to each point of the illuminated area with time. An optical deflecting device characterized by illuminating.

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